Identification And Genetic Analysis Of Synthetic Wheat Improved Strains To Pre-Harvest Sprouting Resistance

Pre-harvest sprouting(PHS)refers to the germination of grains on spikes before harvest.Due to global warming and frequent extreme weather events,the occurrence of PHS on wheat spikes has become more frequent,leading to a significant reduction in wheat yield and quality.Therefore,it is crucial to identify and breed new varieties that are resistant to PHS and utilize them in production.In this study,the germination rate of threshed seeds from 129 synthetic wheat improved strains was tested in six environments(three points in two years)to evaluate their resistance to PHS.The experimental materials were subjected to genome-wide association study(GWAS)using the Wheat55 K SNP array,and their analysis included population structure,linkage disequilibrium,and identification of potential candidate genes associated with PHS resistance.The main findings of this study are as follows:(1)In the PHS identification of parents and populations,2 populations with moderate resistance to PHS and 1 population with no resistance to PHS were identified.Three strains(red wheat strain L2741 and L3006,white wheat strain L586)with stable PHS resistance were obtained.The germination Index(GI)of three stains were 0.12-0.19,0.09-0.19 and 0.1-0.21,respectively.Correspondingly,their germination Rate(GR)were 36%-43%,23%-45%and 24%-52%,respectively.Three strains have resistance level of PHS(GI≤0.2;GR≤40%).(2)Three significantly associated intervals with PHS resistance were identified by GWAS.Marker AX-111317347 and AX-109336147 located on chromosome 5D,which can explain 19.69%and 20.05%phenotypic variation respectively in two environments(2021 Xindu and 2022Chongzhou).The marker AX-111492645(detected in 2022 Chongzhou)located on chromosome 2B,both of its P value and R~2are high,regarded as a significant site.(3)According to the IWGSC Ref Seq v1.0 reference genome annotation,a total of 46 genes were found out within 0.78Mb upstream and downstream of significant markers,4 potentially candidate genes of which were obtained by genes annotation and functional analysis.Traes CS2B03G0865300.1 encodes an F-box protein that regulates plant response to adversity and affects the signal transduction of plant hormones like ABA and GA,thereby influencing seed germination.Traes CS5D03G1120100.1 is a plant lipoxygenase(LOX)that catalyzes the degradation of storage substances during seed germination.Traes CS5D03G1120600.1 belongs to the Squamosa promoter-binding-like protein(SPL)gene family,acting as a cis-acting element in wheat’s drought and adversity stress signaling and participating in the ABA and GA signal transduction process.Traes CS5D03G1160900.1 is a stress-related gene,DUF4220,involved in the ABA signaling pathway,and its over-expression may potentially reduce plant stress resistance.